Wireless communications networks generally allow for voice and/or data communication between wireless stations, e.g., wireless telephones (analog, digital cellular and PCS), pagers or data terminals that communicate using RF signals. In recent years, a number of location-based service systems have been implemented or proposed for wireless networks. Such systems generally involve determining location information for a wireless station and processing the location information to provide an output desired for a particular application.
Examples of such existing or proposed applications include emergency or "911" applications, location dependent call billing, cell-to-cell handoff and vehicle tracking. In 911 applications, the location of a wireless station is determined when the station is used to place an emergency call. The location is then transmitted to a local emergency dispatcher to assist in responding to the call. In typical location dependent call billing applications, the location of a wireless station is determined, for example, upon placing or receiving a call. This location is then transmitted to a billing system that determines an appropriate billing value based on the location of the wireless station. In handoff applications, wireless location is determined in order to coordinate handoff of call handling between network cells. Vehicle tracking applications are used, for example, to track the location of stolen vehicles. In this regard, the location of a car phone or the like in a stolen vehicle can be transmitted to the appropriate authorities to assist in recovering the vehicle.
From the foregoing, it will be appreciated that location-based service systems involve location finding equipment (LFE) and location-related applications. To some extent, the LFEs and applications have developed independently. In this regard, a number of types of LFEs exist and/or are in development. These include so-called angle of arrival (AOA) time difference of arrival (TDOA), handset global positioning system (GPS) and the use of cell/sector location. The types of equipment employed and the nature of the information received from such equipment vary in a number of ways. First, some of these equipment types, like GPS, are wireless station-based whereas others are "ground-based", usually infrastructure-based. Some can determine a wireless station's location at any time via a polling process, some require that the station be transmitting on the reverse traffic channel (voice channel), and others can only determine location at call origination, termination, and perhaps registration. Moreover, the accuracy with which location can be determined varies significantly from case to case. Accordingly, the outputs from the various LFE's vary in a number of ways including data format, accuracy and timeliness.
The nature of the information desired for particular applications also varies. For example, for certain applications such as 911, accuracy and timeliness are important. For the applications such as vehicle tracking, continuous or frequent monitoring independent of call placement is a significant consideration. For other applications, such as call billing, location determination at call initiation and call termination or during handoff is generally sufficient.
Heretofore, developers have generally attempted to match available LFEs to particular applications in order to obtain the location information required by the application. This has not always resulted in the best use of available LFE resources for particular applications. Moreover, applications designed to work with a particular LFE can be disabled when information from that LFE is unavailable, e.g., due to limited coverage areas, malfunctions or local conditions interfering with a particular LFE modality. In addition, the conventional query and response mode of operation between applications and the associated LFEs has resulted in the use by applications of LFE dependent data formats, LFE limited data contents, and single LFE input location determinations.